Google, Eniro, hitta and others

As part of an initial survey for a modelling project, I made a simple comparison over satellite photos of the terrain provided by prominent global actors such as google (Google Maps http://maps.google.com/) and two major Swedish providers, Eniro (http://kartor.eniro.se/) and Hitta (http://www.hitta.se/). Bing's images were nit detailed enough throughout this area.

Above you can see the result on a sample area. Hitta vividly offers the best quality while Eniro's images are of the lowest resolution. The objective here was to determine which source is more appropriate for us in modelling in cases where high-resolution aerial or satellite photos by e.g. Blom or C3 are not available.

Since there was also a need for oblique and facade images, I made an investigation into a wider range of online resources and checked which features were covered by each of them upon studied area. The features I chose for this purpose were 2-, 2.5- and 3-dimentional representations and panoramic views.

Again, Hitta proves to provide the best results. Specifically, the street view feature in Hitta (Gatubild) is distinguished from the other in the sense that it covers almost the entire city while that of Google Maps only has major roads represented and Eniro has no coverage in the area at all. Nevertheless, 2.5-dimentional views of Eniro are more useful than three dimensional map of Hitta for my purpose. The reason is that Hitta's 3d model is semi-automatically created by image sensering and thus does not fully recognize sides, edges and corners of the buildings, contains lots of distorted building volumes and buildings mixed with trees, whereas Eniro's oblique images (Utsikt) are precisely assembled outputs of high-resolution aerial photos.

In the following table, a summary of analysis is given.